Single-neuron connectome of nucleus accumbens.

The nucleus accumbens (NAc) orchestrates a range of critical physiological functions, including reward and motivation, yet single-neuron-level connectivity of its inputs and outputs remains less comprehensively characterized. Here, we examined the organizing principle of input and projection of medium spiny neurons (MSNs) across NAc in adult male mice at single-cell resolution. Our results revealed topographic distribution principles of these neurons and their terminals in the substantia innominata (SI) subdivision. Rabies virus tracing uncovered different monosynaptic inputs to Tac2+ (D1 subtype) versus Calcr+ (D2 subtype) MSNs across NAc subregions. Furthermore, cortical neurons projecting to NAc core or shell showed distinct cortical origins and collateralization. Hippocampal neurons projecting to the NAc preferentially innervate the core and medial shell with longitudinal topography and the strongest co-projection to the hypothalamus. Together, these data delineated the neuronal connectivity patterns of different neuronal subtypes in NAc, providing an anatomical basis for further understanding the neural circuit mechanisms underlying the functional role of NAc.